why are resonance chambers made out of sturdy materials like wood & not out of softer materials like cardboard

Answer 1

Resonance chambers have one goal - to amplify sound by taking advantage of constructive interference. Hard materials are advantageous for two reasons:

1) It is rigid so the amount of longitudinal (sound wave) energy lost (transferred into) the surface is minimized. A soft chamber will cushion sound waves rather than astutely reflect it.

2) Sturdy materials are typically smooth. As such, sound waves are reflected in an anticipated and predictable manner. Porous, soft materials scatter and trap sound. That is why sound-protected rooms are designed with soft, textured walls - to absorb sound.

Answer 2

If you think of a sponge...taking in sound or water...you understand why softer materials won't work...we use egg crating (cardboard) to muffle sound and even around microphones we use sponge to baffle or muffle wind and lisping sounds. Resonance is a refraction of sound...the harder materials such as steel distort sound but wood creates a melodious return. People have created metal guitars but resonance is both unpleasant and harsh....wood such as in fine instruments produces a mellow sound without adding strident vibrations or muffling. Resonating chambers in creatures produce distinctive vocal ranges and if damaged, their calls would be unrecognized by the animal's own kind.

Answer 3

If you're referring to sound waves, it's because softer materials would absorb them, and harder materials would reflect them.